This study will assess the relationship between indications for the yield of abnormal cranial computed tomograms in two different medical settings. The first, a tertiary care university-affiliated hospital, is one of several sources of computed tomographic exams in the Boston area. The second, a community hospital, the Bay State Medical Center, provides the only computed tomographic services for a large part of Western Massachusetts. For both settings we will examine the relationships between indications and yield on a serial basis, and we will use these results for a series of educational programs for house staff and residents at both hospitals. These programs will be designed to study the impact such educational programs have on future utilization patterns for computed tomography. We will also obtain average and marginal cost estimates for several clinical settings.